Below is a live-stream from the large cloud chamber in Microcosm, showing particle tracks as they appear right now in the exhibition. (Operational during Microcosm opening hours.)
The tracks you see are left by particles from the natural radioactivity present in the soil, rocks, water and air and also the particle showers created by cosmic rays from outer space. Such particles also pass through our bodies every second of every day no matter where we are.
Cosmic rays hitting the outer atmosphere of the Earth are mainly fast-moving, high energy protons. As they hurtle towards the Earth, they collide with atoms in the air, creating a myriad of lower-energy new particles, like pions, muons and electrons.
As visitors push the buttons of the cloud chamber in Microcosm, you will see bursts of additional particles appear on the live feed. These come the from radioactive sources - alpha emitters (Radon-220, Potassium-216, and Americium-241) and electron emitters (Strontium-90) - contained within the chamber.
How does it work?
Cloud chambers were one of the first particle detectors used. They are a sealed chamber containing water or alcohol vapour close to point of condensation, making it supersaturated. If any electrically charged particle passes through such environment, the vapour ionises. The ions formed act as points of condensation for the surrounding vapour and visible clouds/mist form along the trajectory of the passing particle.
One can observe different cloud tracks with distinct shapes, depending on the particle type, energy and direction. For example straight thin tracks belong to fast, high energy particles, such as muons and beta particles (electrons and positrons), while thick short tracks are left by the most ionising form of radiation - alpha particles (Helium nucleus). Thin and curved traces show the evidence of deflection of lower energy electrons by collisions with other particles.
Cloud chamber video
In case you cannot visualise the livestream properly, or it is not available, you may watch the short pre-recorded VIDEO .
You can also find out how to build your own little cloud chamber here.